I ride early AM. That is when my glucose level will be the lowest of the day. It takes me about 30 minutes to spend myself at higher PM effort and rates. However if I ride slower (lower heart rate 60% or so) I find I can truck along pretty good (16 - 18 mph) for a good hour or hour and a half without consuming any food. I eat breakfast as soon as I get home and I am set for the day.